Twist-drill.



UNITED STATES PATENT OFFICE.

I GEORGE E. HACKETT, OF ROSELLE, NEW JERSEY.

TWIST-DRILL.

Specification of LettersPatent. Application mea october c, 190e. serial No. 337,811.

Patented Ju1y'14, 1908.

Be it known that I, GEORGE EHAKETT, a citizen of the United States, residing, at Roselle, in the county ofsUnion and State oi" New Jersey, have invented certain new and useful Im rovements in Twist-Drills, ofl

which the 'ollowing is a specification.

My invention has for'its object to provide a form of twist drillof reduced cost and which. may be manufactured from high speed steel, the diihculty of working which has heretofore limited its extensivevuse on account.A of the expense attending its manu# facture by the methodsnow commonly ems ployed. The drill as a whole iswformed:from4 a flat 'blank of prov er. size or shape, which may be lluted or. o anneled if desired, and, which is twisted, both to form the spiral I twist for the cutting body and also to form a 2OA shank, the curvedfexterior surface formed by `the spiral twist ofthe'shank being suitably shaped, either tapered or cylindrical as-1t may be desired; and my'invention also co'nf sists in a drillfhaving its shank so formed'byy twisting a blank. Aspreferably made, :the

shank is tapered to lit a standard twist-drilly socket, but with 'saving of metal by reason of the skeletonized character of the shank portion.

In the accompanying drawin s,Fig-urei1,

is va side elevation of a drill ma e inv accord` ance with this invention by the process herein described. Fi 2, is an elevationof the point thereof, an Fig. 3, is an elevation of the shank.

, In car out my invention I take af sultan@ dani( the same, the pitch ofthe twist bein deter# of suitablev shape andv twist mined by the materialupon which t e is to be used and by other factors well understood in drill designngrflt is obvious that the pitch may be varied .from point to oint alon ,esired .drill vary the pitc the length ofthe drill as. may be ofthe twist of the body in proportion to the bending moment at the corresponding increased strength is` obtained, as jby. de

creasing the pitch the, slpirals are brought more into parallelismwit the force tending to prevent lrotation of the drill, or toun.-

i twist it and more points of contact are :ro-A

vided' between theV shank and socket. @et

but the Shank also only is the body part. ofthe drill'fmade by` twisting the blan made-by twisting, ,thereby much reducing' rolling.

points of the drill whereby .may be producedl `the :cost of manufacture over drills Awhose Shanks are made by turning, -grinding or v It 1s obvious thaty the taper of theshank may be obtained by a unlform twist of a proper blank, the shank forming Aend of which is a trapezoid, or by aunform twist tangle and' by subsequent grinding,:but to cheapen construction I prefer to make the drill including the body, and shank of a sinfg'lefrectangular blank, and to provide for va'- y rlationol` diameters along the drill and shank and the taper of the shank produced by a* uniform variation of th. twist along' its` `oa blank whose shank formmg end is a rec'-l length. Obviously these variations of die ameter by a variationl of the pitch .of .the twistv may also take place 1f desired along. the

bod. portion of the drill. AInthis way the dril as produced by the twisting may be caused to approximately correspond to its. desirediinished diameter whereby the amount of grinding necessary to complete it maybe ter twisting, is, .Itol have its surface accurately shaped by' greatly reducedifthe drill, a

grinding. The tip of the shank is preferably left untwisted so as toprovidethe usual tan may be so-formed by grindmg or forging, or otherwise as willadapt it tothe material'to be operated on and that the blank itself may be channeled or grooved if desired to groove of the iinishedI drill and that the drill, including shank and'body', may be iin-l ished by grinding in any desired manner, mv

of a`drillj`from a suitable blank bytvlistin'g it in theann'er. before described and a varia-.-

tion-"of thepitch of the twist to cause the `drill produced byjsuch'twisting'to have at various points different diameters, whereby 'the amount 'of-grinding, if any be necessary to finish-the drill, isredu'ed. A

While the drill: shown in the accompanying l'drawings is adapted-lor u'sejon metal, it is obvious that b proper designing y the process herein deg ywith side'sparallel-'to the axi's'of ythe drill.A It'v zisurther obvious that the point ofthe-drill pro-- 'duce' ajcorrespondin'g crossl sectlon of the ico improved process contemplating the making` ros 5 not severed or diseemeeefl in the -vRecess of making the drill, but emayiu continuous the'em, and tlmt'lihe dmmete el". the dmll, elther 1n the becly or shank, may be Varied 'Without severing the bers et the peints of le reduction.

y Having thus described mv invention what I ela-im :md desire te secure by Letters l?n.tent is:

S e new and improved article of menufaelnule the l'lereill described drill having n, twisted bedy portion :md :L twisted tapered. shank, the sllmll having n, twist of inermiA ing pitch.

` GEORGE E. llAllE'llT. Vlltnesses WHLMAM HAWKINS, WELMNG 'M .PERMN'LL 

